Mold



Patented Get. 28, 1924.

I uurrso STATES PATENT OFFICE.

FRANK J. TONE, OF NIAGARA FALLS, NEW YORK, ASSIGNOR TO THE CARBORUNDUMCOMPANY, OF NIAGARA FALLS, NEW YORK, A CORPORATION OF PENNSYLVANIA.

MOLD.

No Drawing.

To all whom it may concern:

Be it known that I, ERANK J. TONE, a citizen of the United States,residing at Niagara Falls, in the county of Niagara and State of NewYork, have invented a newand useful Improvement in Molds, of which thefollowing is a full, clear, and exact description.

This invention relates to molds, and particularly to permanent moldssuch as are used for casting metals. Generally speaking,

tWo general classes of molds for use in casting metals are in commonuse. The use of silica sand, moistened with water or mixed with variousorganic binding agents is well known. lhe use of dies made of steel orplaster of Paris is also quite extensively practiced, particularly forcasting the lower melting alloys. Steel molds or parts of molds havealso been used for the production of cast iron articles, such as sewerpipe, but these are generally unsatisfactory because the surface ischilled and is so hard that cutting or shaping is almost impossible.

I have discovered that silicon carbide grains made into proper shapes bybondin with suitable binders and vitrified to a soli body may beadvantageously used in many cases to replace either the sand, metallicor other molds now in common use, especially in the making of permanentmolds, that is, molds which are used for more than one casting operationWithout being broken up in a manner similar to sand molds. Theparticular property of silicon carbide which makes it highly suitable inthe making of permanent molds for casting is its high thermalconductivity, which is about eight times that of molding sand whenformed into the molds commonly used in casting. The thermal conductivityof silicon carbide .is, however, only about one-third that of iron.

For rapid work and satisfactory production, a material for making apermanent mold should be able to carry away heat from the fluid metalfast enough to bring the metal of the casting to a solid conditionin amuch shorter time than is the case in sand molds, so that the mold canbe opened, the casting dropped out, and the mold then closed u againready to pour the next casting. owever, it should not have such a highthermal conductivity that the casting is chilled and converted intochilled iron on its surface or throughout the casting. I

form, as for example, by

Application filed May 26, 1923. Serial No. 641,766.

essary to produce this result, and is unique in this respect of standingmidway between the metals and other mineral substances in the scale ofthermal conductivity.

When properly bonded into permanent my process disclosed 1n UnitedStates Patent No. 1,204,211, November 7 1916, silicon carbide refractoryblocks have great strength, not only at ordi nary temperatures, but evenat the highest temperatures attained in the casting of the common metalsand alloys. The molds thus made have great resistance to temperaturechanges and do not crack, spall, warp or distort in shape.

As distinguished from sand molds, which may be used for a single castingonly, bonded silicon carbide molds under suitable condtions may be usedrepeatedly in the form of permanent molds, thus saving the labor ofmolding. Iron or other metals cast in silicon carbide molds do not stickto it, thus saving the labor of cleaning the casting. Since the moldsare already vitrified they do not give off gas as'does a sand mold, andone of the principal causes of unsound castings is therefore removed.While steel and metal molds may be used over and over, theircost,especially for intricate designs, is much greater than for similar moldsmade from silicon carbide and a bonding agent, as above described.

As a preferred method of making this form of mold, I take a mixture often parts of highly refractory clay and ninety parts of silicon carbidegrain of mixed sizes from 14 mesh to the finest powders. This mixture ismoistened with water and worked into the v desired shape. It is thendried and burned at reduce the rate of cooling the casting by reducingthe amount of silicon carbide and increasing the amount of ceramicbinder.

While I have described my invention as a mold for casting, it will beunderstood that I use this term in a general sense, it being parts ofsilicon carbide and 10 parts of a ceramic binder.

4:. A permanent mold for casting comprising a vitrified mixture ofsilicon carbide and a ceramic binder, the silicon carbide being insuliicient proportion to give it a thermal conductivity greater than asand mold.

A permanent mold for casting comprising a vitrified mixture of siliconcarbide and a hinder, the silicon carbide being in grains of varyingsizes.

6. A permanent mold for casting comprising a vitrified mixture ofsilicon carbide and a binder the silicon carbide being in grains ofvarying sizes but none larger than 1 mesh. I

In testimony whereof I have hereunto set my hand.

FRANL 'LGNE.

